Feature/collisions quadtree

example/lib/src/common/widget/routes.dart

@@ -3,6 +3,7 @@ import 'package:repaintexample/src/feature/clock/clock_screen.dart';
 import 'package:repaintexample/src/feature/fps/fps_screen.dart';
 import 'package:repaintexample/src/feature/home/home_screen.dart';
 import 'package:repaintexample/src/feature/performance_overlay/performance_overlay_screen.dart';
+import 'package:repaintexample/src/feature/quadtree/quadtree_collision_screen.dart';
 import 'package:repaintexample/src/feature/quadtree/quadtree_screen.dart';
 import 'package:repaintexample/src/feature/shaders/fragment_shaders_screen.dart';
 import 'package:repaintexample/src/feature/sunflower/sunflower_screen.dart';
@@ -45,4 +46,9 @@ final Map<String, Page<void> Function(Map<String, Object?>?)> $routes =
         child: const QuadTreeScreen(),
         arguments: arguments,
       ),
+  'quadtree-collisions': (arguments) => MaterialPage<void>(
+        name: 'quadtree-collisions',
+        child: const QuadTreeCollisionScreen(),
+        arguments: arguments,
+      ),
 };

example/lib/src/feature/home/home_screen.dart

@@ -48,6 +48,10 @@ class HomeScreen extends StatelessWidget {
                     title: 'QuadTree',
                     page: 'quadtree',
                   ),
+                  HomeTile(
+                    title: 'QuadTree collisions',
+                    page: 'quadtree-collisions',
+                  ),
                 ],
               ),
             ),

example/lib/src/feature/quadtree/quadtree_camera.dart

@@ -0,0 +1,112 @@
+import 'dart:ui';
+
+import 'package:repaint/repaint.dart';
+
+mixin QuadTreeCameraMixin {
+  final QuadTree quadTree = QuadTree(
+    boundary: const Rect.fromLTWH(0, 0, 100000, 100000),
+    capacity: 18,
+  );
+
+  final _camera = QuadTreeCamera(
+    boundary: Rect.zero,
+  );
+  Rect get cameraBoundary => _camera.boundary;
+  Size size = Size.zero;
+
+  bool needsPaintQt = false;
+
+  void mountQtCamera() {
+    _camera.set(Rect.fromCenter(
+      center: quadTree.boundary.center,
+      width: size.width,
+      height: size.height,
+    ));
+  }
+
+  void updateCameraBoundary(Size newSize) {
+    size = newSize;
+    _camera.set(Rect.fromCenter(
+      center: _camera.boundary.center,
+      width: size.width,
+      height: size.height,
+    ));
+    needsPaintQt = true;
+  }
+
+  void moveQtCamera(Offset offset) {
+    if (offset == Offset.zero) return;
+    needsPaintQt = true;
+    _camera.move(offset);
+    // Ensure the camera stays within the quadtree boundary.
+    if (_camera.boundary.width > quadTree.boundary.width ||
+        _camera.boundary.height > quadTree.boundary.height) {
+      final canvasAspectRatio = size.width / size.height;
+      final quadTreeAspectRatio =
+          quadTree.boundary.width / quadTree.boundary.height;
+      if (canvasAspectRatio > quadTreeAspectRatio) {
+        _camera.set(Rect.fromCenter(
+          center: _camera.boundary.center,
+          width: quadTree.boundary.width,
+          height: quadTree.boundary.width / canvasAspectRatio,
+        ));
+      } else {
+        _camera.set(Rect.fromCenter(
+          center: _camera.boundary.center,
+          width: quadTree.boundary.height * canvasAspectRatio,
+          height: quadTree.boundary.height,
+        ));
+      }
+    }
+    if (_camera.boundary.left < quadTree.boundary.left) {
+      _camera.set(Rect.fromLTWH(
+        0,
+        _camera.boundary.top,
+        _camera.boundary.width,
+        _camera.boundary.height,
+      ));
+    } else if (_camera.boundary.right > quadTree.boundary.right) {
+      _camera.set(Rect.fromLTWH(
+        quadTree.boundary.right - _camera.boundary.width,
+        _camera.boundary.top,
+        _camera.boundary.width,
+        _camera.boundary.height,
+      ));
+    }
+    if (_camera.boundary.top < quadTree.boundary.top) {
+      _camera.set(Rect.fromLTWH(
+        _camera.boundary.left,
+        0,
+        _camera.boundary.width,
+        _camera.boundary.height,
+      ));
+    } else if (_camera.boundary.bottom > quadTree.boundary.bottom) {
+      _camera.set(Rect.fromLTWH(
+        _camera.boundary.left,
+        quadTree.boundary.bottom - _camera.boundary.height,
+        _camera.boundary.width,
+        _camera.boundary.height,
+      ));
+    }
+  }
+
+  void unmountQtCamera() {
+    quadTree.clear();
+  }
+}
+
+class QuadTreeCamera {
+  QuadTreeCamera({
+    required Rect boundary,
+  }) : _boundary = boundary;
+
+  /// The boundary of the camera.
+  Rect get boundary => _boundary;
+  Rect _boundary;
+
+  /// Move the camera by the given offset.
+  void move(Offset offset) => _boundary = _boundary.shift(offset);
+
+  /// Set the camera to the given boundary.
+  void set(Rect boundary) => _boundary = boundary;
+}